Arc lamp electrode regulating system and mechanism



25, 1946. A SHELDON 2,402,922

ARC LAMP ELECTRODE REGULATING SYSTEM AND MEGHANISM Filed April 7, 1941 ZSheets-Sheet 1 Inventov: Lyle Ahelclon,

by HIS Attorney.

June 25, 1946. L. A. sHELDoN 2,402,922 ARC LAMP ELECTRODE REGULATING SYSTEM AND MECHANISM I Filed April '7, 1941 v 2 Sheets-'sheet :e`

His Attorney.

Patented June 25, 1946 ARC LAMP ELECTRODE REGULATING SYSTEM AND MECHANISM Lyle A. Sheldon, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application April 7, 1941, Serial No. 387,372

(Cl. S14-79) 12 Claims. 1

My invention relates to arc lamps, and more particularly to electrode regulating systems and mechanisms, for arc lamps such as are used in searchlights yand similar light projectors.

One object of my invention is to provide an electrode regulating system and mechanism which is responsive to slight changes in arc characteristics.

Another object of my invention is to produce an electrode regulating system and mechanism which will automatically move the electrodes to a starting position after the arc lamp is shut down so as to reduce the time required to start the arc after the next closure of the operating switch.

For a better understanding of my invention, together with other and further objects thereof, reference is had to the following description taken in connection With the accompanying drawings, and its scope Will be pointed out in the appended claims.

In the yaccompanying drawings, Fig. 1 is a dagrammatic illustration of the electrodes, the supporting mechanism therefor, together with the shafts for operating the mechanism, and a diagrammatic illustration of my improved regulating system and mechanism for actuating the electrode mechanism. The shafts transmitting the rotary motion, from the actuating mechanism, and the corresponding shafts at the electrode mechanism which receive this rotary motion are broken off at the respective mechanisms and are, lfor the sake of simplicity, connected by dot and dash lines to illustrate this mechanical connection between the corresponding shafts. The electrodes and the supporting mechanism are placed at the focal axis of a light reflector while the actuating mechanism is placed at a distance from the electrode mechanism, preferably on the surface of an enclosing drum which surrounds the electrode holding mechanism and the reflector. The angular relationshipy between the actuating mechanism and the electrode supporting mechanism varies for different searchlight structures and it is therefore to be understood that the shafts at the actuating mechanism and the shafts at the electrode supporting mechanism may be one and the same shaft or may be connected mechanically in any suitable manner to transmit rotary motion from the actuating mechanism to the electrode supporting mechanism. Fig. 2 is a modification of the electrode feeding system and mechanism as illustrated in Fig. l.

Referring to the drawings in detail, Fig. 1 illustrates a positive electrode I and a negative electrode Il. The negative electrode is supported in a conventional manner by a brush I2 and a pair of feed rollers I3, I3'. The feed rollers are respectively mounted on shafts M, I4 upon which are mounted engaging gears I5, I5. The gears I5, l5 are driven by a Worm I6 mounted on a shaft Il. The shaft l1 is driven by my improved regulating system and mechanism to advance, or to retract, the negative carbon thereby to start and to maintain constant an arc between the tip of the negative electrode and the crater in the end of the positive electrode.

The positive electrode, as illustrated in Fig. 1, is mounted in a conventional mechanism for con stant rotation during operation and for intel mi'ttent axial movement to maintain the crater in a predetermined position. The supporting mechanism, `which is only diagrammatically illustrated, includes a U-shaped frame 20 mounted on the end of a guidesleeve 2|. A bevel gear 22 is mounted on the other end of the sleeve 2l an-d is engaged by a gear 23 mounted on the end of a drive shaft 23. This shaft 24 is driven at a constant speed during the operation of the arc lamp to rotate the frame 26 and the positive electrede supported thereby.

The positive electrode I@ projects from the guide sleeve 2l into the frame 23, the projecting arms of the U-shaped frame being parallel tothe electrode. The electrode is supported in the frame by a pair of feed rolls 25, 25 mounted respectively on shafts 26, 2K6', the shafts being mounted in the frame 23. The shafts 26, 26 are connected through a system of gearing to a drive gear 21 loosely mounted on the sleeve 2l. This system of gearing may be traced from the interengaging gears 28, 28 mounted on the shafts 26, 26 respectively to gear 29 mounted on shaft 26, thence to gear 30 mounted on a shaft 3l upon Which is also mounted a Worm gear 32 driven by a Worm pinion 33 mounted on a shaft 34. The -shaft 34 is mounted transversely of the shaft 3| and has mounted upon it a pinion 35 which is in engagement with the drive gear 21. The shafts 26, 26', 3l and 34 are all supported by the frame 2U and during rotation of the frame move with the frame. The shafts and the gears do not rotate about their own axes unless there is a relative rotation between the sleeve 2l and the drive gear 21. To produce such relative rotation between the sleeve 2l and the gear 21, the gear 21 is attached to a notched disk 36 which may be stopped by a pawl 31. The notched disk, which is similar to a ratchet Wheel, is attached to the gear 21 by pins 38 so that it will rotate with the drive gear 21 about a common axis. The paw] 31 is mounted upon the end of a shaft 39 and may be moved into and out of the path of movement of the disk by moving the shaft 39 about its axis. When the pawl 31 is moved into the path of the disk 36, it moves into one of the notches of the disk and holds the disk and gear 21 stationary. The pinion 35 is thereby forced to roll over the periphery of the gear 21 thereby rotating 'the shaft 34 and effecting, through the system of gears above described, a rotation of the feed rolls 25, 25' to advance the electrode Ill. To stop such advance movement, the pawl 31 is moved out of the path of the dislo 36 to allow the disk to move with the sleeve 2|.

The mechanism so far described is one form of such mechanism commonly used. It is spaced from the actuating mechanism to which it is connected by shafts I1| 24, 39. The apparatus and system for operating the shafts I1, 24 and 39 of this mechanism is built in accordance with my invention and, for the sake of simplicity in the drawings, the shafts I1, 24 and 39 are broken, one end of each shaft being shown at the electrode holder and the other end of each shaft being shown at the operating apparatus. The two ends of each of these shafts are not axially aligned in this diagrammatic illustration but are connected by dot and dash lines. It is to be understood that in actual installations the shafts are either continuous or are mechanically connected, in any suitable manner, to transmit the rotary motion of the shaft at the driving apparatus to the similarly designated shaft at the electrode holders.

The system and apparatus for driving the shafts I1, 24, 39, as diagrammatically illustrated, includes a motor 4I) which is energized during the operation of the lamp. This motor is connected, 'through its shaft 4I and a pair of engaging gears 42 and 43, to drive a shaft 44, the gear 42 being mounted on the end of the motor shaft, and the gear 43 being mounted on the end of the shaft 44 which is supported in any convenient manner (not shown). The movement of the shaft 44 is transmitted to the negative electrode feed shaft L.

I1 by a clutch device including a friction disk 45 mounted on the end of the shaft I1 and drive pinions 46 and 41 arranged to engage alternative ly the friction disk 45 at diametric opposite points. The pinions 46 and 41 are attached to opposite ends of a sleeve 48 mounted on the shaft 44 and in driving engagement with the shaft 44 through a driving pin 49 mounted in the shaft 44 and projecting through a slot 50 in the sleeve. The pinions 46 and 41 comprise the armatures of magnets I and 52 respectively. When the coil of magnet 5I is energized, it attracts its armature 46 and through the sleeve 48 pulls the armature 41 into frictional driving engagement with the edge of the disk 45, this armature then operates as a. friction pinion and drives the shaft I 1 in one direction. When coil 52 is energized, it attracts the armature 41 and through sleeve 48 effects an engagement of the armature 46 with the disk 45, the armature 46 then operates as a friction pinion to drive the shaft I1 in an opposite direction.

The magnet coils 5I and 52 are, in accordance with my invention, energized from a potentiometer through contacts operated by a magnet coil connected, preferably, in series with the arc current and therefore responsive to variations of the arc current. In some cases it may be satisfactory to use a magnet coil connected across the electrodes and therefore responsive to variations of the arc voltage. The potentiometer circuit may be traced from the power switch 55 illustrated in the lower right-hand corner of the drawing as a double-pole single-throw switch arranged to connect a suitable source of power, indicated merely by the plus and minus terminals, to power supply conductors 56 and 51. The potentiometer, comprising a resistor 58, is connected at one end through a conductor 59 to the conductor 56 and at its other end it is connected through a conductor 60, contact 6I, brush 62 and a conductor 63 to the supply conductor 51. The circuits to the regulating magnet coils 5I and 52 are controlled by a coil 64 which is connected in series with the arc current and is preferably referred to as the current coil. This coil is a spirally wound copper bar having a relatively large cross section so as to carry the entire arc current with little loss. The circuit of 'this coil 64 may-be traced from the positive supply conductor 56 through a conductor 65 to the positive electrode I0, through the arc to the negative electrode II, conductors 66 and 61 to one end of the coil 64. The other end of the coil is connected to supply conductor 51 through a conductor 68. The current coil 64 is provided with magnet poles 69, 10 between which an armature 1I attached to a pivoted arm 12 is positioned to move relatively to the pole faces in accordance with the magnetic force crea-ted by the current flowing through the coil 64, The arm 12 is pivoted upon a knife edge support 13 and has at tached to one end, thereof a spring 1,4 the tension of which may be adjusted by an adjusting screw 15 mounted in a fixed support. The tension of this spring is balanced against the magnetic force exerted upon the armature 1I. An unbalance between these two forces effects a movement of armature 1I which in turn effects a movement of a group of contact fingers mounted upon the free end of the arm 12,

The contact ngers mounted upon the free end of the arm 12 comprise resilient metal strips spaced from each other by insulating blocks and arranged in pairs on the upper side and the lower side of the moving arm 12. A stationary actuating arm 16 is positioned between pairs of the contact fingers so that a movement of the arm 12 and 0f the contact ngers effects an engagement between pairs of the contact fingers, to close corresponding circuits of the magnet coils 5I, 52. In the arrangement illustrated a pair of resilient contact fingers 11, 18 is mounted on the under side of the arm 12, the contact fingers being spaced from each other by an insulating block 1B. An upward movement of the arm 12 moves the end of contact finger 11 into engagement with the stationary actuating arm 1.6 and holds the end of that contact nger stationary until a further movement of the arm 12 moves the contact ringer 18 into engagement with the Contact 11. Suitable contact tips are provided on the ends of the resilient contact fingers to provide the engaging surfaces through which current may pass from one contact finger to the other. Similar contact ngers 19, 8D and 8| are mounted on the upper side of the arm 12 and are brought into engagement with each other upon a downward movement of the supporting arm 12.

The supporting arm 12 moves the contact lingers 11, 1B upwardly when the current in the coil 64 falls below a predetermined value, The spring 14 then overcomes the pull of the poles 69, 19 and effects a closure of the circuit between contact fingers 11, 18 and a completion O1' the circuit to coil 52. The circuit for coil 52 may conductor'V 83to a ta'p Bilr on thepotentometer resistor 58. The contact finger T1 is connected to a tap 85 on. the ,potentiometer resistance through a conductor i The coil 52 is therefore connected across that portion of the potentiometer resistor 58 which is between the taps 84 and 85. The coil 52y being,y thus. energized, attracts its armatured'l and throughthe sleeve 48 pullsthe armature" 46, into driving engagement with the disk, 45. "Thisoperation being due to a reducn tion in arc current, the coil 64 is arranged to effect a rotationof thedisk 45 and shaft in a directionto eiect a correspondingv forward movement of theneggative electrode to reduce the arc length and its resistance, thereby to increase the current to normal value. W hen such normal current value is reached, the pull of the poles 69, l!) overcomes the pull of the spring 14 to move the armJZ downwardly and thereby to separate the contact finger ll,v 18. The coil 52 then becornesJv deenergizedvand nolonger pulls the armaturelii in to frictional engagement with the disk 45. Thel driving relationshipbetween armature Scand disk dis thereby broken, the armature M cont'inuingto yrotate.without moving the disk 45' I In casev the current in current coil d rises. abovea vpredetern'ifinedv value, the arm l2 is pulled downwardly. Thecontact finger 'I9 then engages the stationary actuating armY 16 and a' further ro. .veurient of thevarrn l2- moves the contact nn.- ger Si! into engagement with the contact linger 1s ip close 'the circuit. to the coil es; This cir;

cuit 'may bel traced from the Contact iinger i9 thl'ugh the conductor 85 to the potentiometer tap 35:. The` Contact finger 'Bil is connected through a. conductorV 8,1 to. one terminal ofY the coil: 5|: and.. theA other terminal ofthe coil 5| is conhectedthrough.conductors 8,8, 83 tn thepo` tentiometer tap 34. Thisroperation ofthe pivoted arm 'L2 therefore energizes the coil 52, this coil also being connected across that portion of thepotentiometer. resistor '518.2 between the taps 84 and' 85.y v 'Ivfhe coil 5| then attracts its armaturenlhand tlirough sleeve 48 pulls the armature 41 Vinto drivingbengagement with the disk 45. The shaft 4,4, operating in one direction only, now drives the armature` 4J. in the same direction7 as it drives the piniondllibutthe engagement with they disk. 5. a diametrically opjrjositeV4 point and therefore thedisli 4,5, and the. shaft, l1 are reversed in direction to effect a retraction. of the electrode and a lengthening or".v the arc between the electrodes in and l.

Inv case the current increases in coil @A to a still higher value than in the previous operation, the arm 'I2` is pulled, downwardly until a circuit is established between the three contact ngers 79:, S0 and 8|. v'lihe contact :fingers 19, 8i? have already established a circuit between the retract@ ingl coil lil. and the potentiometer, and the additional circuit esrahlishedfthoueh contact iin ger si establishes anoiherjciiciiii to tu@ paientionweter which may. beA traced from supply conduct r 5 5` through'a conductor, 88, through con.- tac lingers 8J', Elfi, lll, and from the contact iin- 1Q through conductor lili to, 85: on the po ntigmeter' resista;ree,` IIjhis circuit makes inl M t portion of the potentiQmeter. reH Ssan whih'is between the tan 8,5, and the conductor 59 thereby places, thel electrode po t'alfacr` s Athe remaining portion of the rerThis op ation places a 'greater portion of the available potential upon the coil 5| and isused, only when the current in the current c'il- B4 rises to values attained when the two electrodes l0 and are substantially in contact with each other. This usuallyoccurs at thestart` ing operation of the arc. The potential drop between the electrodes is lowat that instant and` a reduction in the potentiometer resistance is necessary to obtain suiicient potential acrossthe' coil 5| to insure a good drive connection between the pinion lil and the disk 4 5to retract thefnegaly tive electrode as duicklygas possible.

It is above pointed out that the potentiometer circuitincludes a disk E! and a brush 62. The` diskli! isfmountedupon a shaft Pifoperable by a cranks! which isprovided to operate the's'liaft Il byhand. To eifectvsu'ch operation the shaft Siilwismoved axially through'a support'd against thel pressure of a spring, 95 to eifect an enga`gement between a pair of bevel gears 92, vinland to eiect a separation ofthe disk 5|y and the brush 62; This operation simultaneously akes ineffec-l tive thef electrical` controlv` for the shaft" Il and establishes a mechanical controlv between' thel shaft T and theshaft Il; the gear 9 2 being mounted Onthe shaft 9|) andl the gearvbene' mounted on the shaft l1. This establishs a handl control fOr the shaft H, from thecrank'. lil which is used to make quickly adjustments that may become necessaryv when new ca ibonsfV are'rplaced'into-the lamp. The positive electrode mechanisml isv actuated by the motor 4 5 through a worm pinion Hill, mounted. on an extension of the, motor shaft op'PQ'SCG to thev extension uoon vwhich the 'pinion 4...@ is mounted The. pinion lill! engages a Wohle gear lillprhich. through a ball clutch H22, drives a shaft liif', The shaft. m3 drivesva shaft 2liA of thepositiveelectrode rotavtiner mechanism throug'h a-ear 0f beveled sears IM, "i5" The rotation f. th shaft 24. effects a constant rotation of the positive electrode, lil during` the operation of the arc lamp.k The motor 4b is connected to thfej` supply conductors 56y and 51 in parallel'-with the electrodes mand by a circuit which may be traced as follows: Supply conductor 5B, conduct# tcr 65, conductor H25, motor MB, conductorV Si, conductor 5], magnet coil M; and conductor 6,8lv to., supply conductor 5l, Thus'motor lllllis al ways' running when the. lamp, circuit is closed,

The positive electrode is advanced at regular intervals by a periodic operationof the pawl shaft 39; This shaft actuatedby an electron'iag'lr'i-etl coil |01 provided with pole pieces Hi8,r |03 and with an .ar-matureI i iii. attached to, the` end of the pawl shaft 39 A spring'lil attached to tlileypgole'A piece Bimby, a pin H19] and to one side' of, the armature illlhy a pin H2l pulls the armature and itsY shaft 39 intoa position in which thepawll is out or the para of. the disk at asv ii'iustratedY iii Fig. 1. The armature il!! in this position is: at an angle to the nflagneticl path between theV pole The ein H2 attached t@ the armature Uil. Droects downwardly to engage the, end of.

an, adii1ste-ble pin |13 which serves as a stop to determine this in'aCtiverositi-oti of. the. armature, the |573 beingv supported in aV lug |43 projectf ing from. theinaenet frame. Upon energization of the coil. U31 the armature. lill rotates, against the lpull of thespr-ing |l|| and movesinto a posinon to align 'itself with the, magnetic field between the pole faces. The pawl 31 correspondingly moves into the path of movement ofthe disk 3S;t and stops rotation of this disk and the attached gear 21. V`The electrode mechanism con- 7 tinues to rotate, being driven by the shaft 24, and the driving pinion 35 is forced to roll over the gear 21, thereby advancing the positive electrode through the system of gears above described. This operation continues only as long as the pawl 31 engages the disk 36.

The coil |01 is intermittently energized, to effect engagement by the pawl 31 of disk 36, by an adjustable contact mechanism so that the lntermittent advance of the positive electrode may be adjusted to equal the rate of consumption of the electrode. 'I'his intermittent energization is obtained through a pair of contact fingers I I4 and H5 operated by a cam H6 mounted on the continuously rotating shaft |03. The circuit between the coil |01 and the contact fingers H4 and H5 may be traced from conductor 56 to coil |01 through conductor |24, through the coil, through conductor |25, contact fingers H4, H5, through conductor |26 to supply conductor 51. The cam I I6 engages the contact finger H4 for a predetermined period during each revolution of the shaft |03 to move the contact nger H4 into engagement with the contact ringer H5 and hold it in engagement for this predetermined time. The contact fingers H4 and H5 are provided with suitable contact tips, are spaced from each other by an insulating block I1 and are supported by a block IIB. The block H8 is pivotally mounted by a pin H9 and is held in a stationary position about this pivot by a spring against an adjustable cam I2I. The cam I2| may be adjusted by a. shaft |22 having thereon a position-indicating knob |23. The shape of the cam I2I is such that a movement of the shaft |22 about its axis effects a movement of the block I |8 about its pivot H9 against the tension of the spring I 20. The contact fingers H4 and H5 projecting from the block to a position under the cam I I 6 are thereby moved nearer to, or farther from, the axis of rotation of the cam H6. A movement of the contact arms nearer to the axis of rotation of the cam I I6 increases the period of time, during each revolution of the cam H6, during which the contacts H4 and H5 are in engagement with each other. A movement of the contact arms away from the axis of rotation of the cam I I6 decreases the time during each revolution of cam H6 during which the contacts H4 and H5 are in engagement with each other and thereby the rate of the intermittent feed of electrode I0 is reduced. This cam H6 and shaft |03 may also be operated by a hand crank :mounted on a shaft I3I. The shaft |30 supports one half, |32. of a coupling and may be axially moved against the pressure of a spring |33 to effect an engagement of the coupling half |32 with a second coupling half |34 mounted on shaft |03. The ball clutch |02 will release the gear |0I to permit a movement of the shaft |03 in a direction to advance the positive electrode.

One of the main advantages of the system and apparatus above described is its improved sensitivity to changes in arc current. The actuating coils of the negative electrode feeding device being connected across a portion of a potentiometer resistor are responsive to a fraction of the normal arc voltage and in case of low voltage, such as occurs at starting, contacts are provided to place this entire voltage upon the coil to produce substantially normal excitation.

A second important function of my improved mechanism is the automatic advancement of the negative electrode into substantially starting position after a shutdown of the arc lamp, When the main line switch 55 is opened, the arc current ceases to flow and the motor 40 is deenergized. The motor continues to rotate, however, due to its inertia. The current coil 64 at this instance is deenergized because the current in the arc has ceased to iiow and the spring 14 effects a closure of the contacts 11, 18, which Contact closure establishes a circuit from the potentiometer resistor to the magnet coil 52. If at this instant a suitable current is provided across the potentiometer resistor, the coil 52 will be energized and will effect a closure of the clutch, whereby the kinetic energy of the motor will operate the electrode mechanism to advance the electrode ID until the kinetic energy of the motor 40 is spent. Such current for the potentiometer resistor and for energizing the coil 52 may be obtained by utilizing regenerative current from motor 40, by utilizing an auxiliary source of current or by a combination of the two. In the present instance, it is assumed that the motor 4i), when switch 55 is open, has sufiicient inertia to actuate the mechanical parts connected to it but is not capable in addition thereto of supplying the needed current for the potentiometer resistor and the coil 52. Accordingly, provision is made whereby such current is obtained from an auxiliary motor |21, which is a Ventilating motor in the present instance and is connected across the conductors 66 and |06 to drive a Ventilating fan positioned Within a casing (not shown) in which the electrode mechanism is placed. This motor is normally larger than the motor 40 and the Ventilating fan, acting as a fly wheel, adds considerable inertia to the armature of this motor. This additional inertia causes the motor to continue to rotate at a substantial speed and for a substantial time period subsequent to the opening of the switch 55 and to regenerate current sufhcient to energize the coil 52. The circuit for this motor may be traced from one terminal of the motor to conductors 66 and 61, coil 64, conductors 68, 51, 63, contact 62, disk 6I, conductor 68, potentiometer resistor 58, conductors 59, 56. 6'5 and |06 to the other terminal of the motor. It will be noted that the current coil 64 is included in this circuit. The current from the motor is too small, however, to effect a separation of the contacts 11, 18. The clutch coil 52 thereby remains energized until the kinetic energy of the motor |21 is spent. As a result of this operation the negative electrode II is moved towards its starting position and by proper dimensioning of the kinetic energy of the two motors the electrode I is moved to substantiaily starting position. Upon reclosure of the switch 55, therefore, substantially no time is lost in rst advancing the electrode to the starting position. By this arrangement the starting time that is the time between the closure of the switch 55 and the actual ignition of the arc may be reduced substantially. For example, it may be reduced from a period of about 10 seconds to a period of approximately 3 seconds. This is a very important advantage in searchlight operation, especially for certain purposes.

In some instances where no auxiliary motor is available or the auxiliary motor is too small, for providing the regenerative current necessary to energize the coil 52, a motor 40 may be utilized having sufcient inertia to provide not only the mechanical power necessary to operate the electrode advance mechanism but also to provide a part of, or all of, the regenerative current. To increase the inertia of the motor 40 a larger capacity motor may be provided or the armature inertia of the smaller motor may be increased by the ap- 2 is similar .toFigv'L having corresponding elementsdesignated by the. same numerals. It diifersfrom Eig. l in that no fan motor is provided andy-thetcurrent needed to energize coil52 is supplied by the motor lit, the regenerating circuit for themotor iii beingl the sameas that for motor |21, each being connected to the conductors 66 and |955.. A flywheel i555 illustrated in section is mounted onthe shaft it! to provide-the additional inertia l'el'llirdf Fig. 2 also differs fromFig. l in that a normally intermittent energization for the coil 52 is provided; This intermittent operation is obtained byv the,Y provision of a secondl cam |35" upon the continuously rotating shaft |93, togetherwitha( pair of contacts i3? i831 actuated by the cam to provide-the intermittent closure o f the circuit for coiltSZ, thereby to effect an intermittent advance ofi the negative electrode Il. The circuit may be traced from thecoil 52 through conductor 32 to thercontaet, l, from the contact '18.to contact I?, through a conductor L39 to the contact i378, through contact It?, conductor Mi) back to conductor, This circuit merely introduces anintermittentlyA closed pair of contacts in order to intermittently energize the coil 52 and thereby to effect an intermittent advance of the negative electrode. In connection with this mechanism a third contact arm lli-l may be provided below the contact 'i8 and spaced therefrom by an insulating block;v L42. A slight reduction in current in the current coil fifi will effect aclosure of the contacts 11, and 'f8 and a greater reduction in current in this coil-will effect aclosure between contacts 'iii and lili, thereby shunting out the intermittent feed and introducing a constant feed as in Fig. 1. This additional arrangement of contacts, therefore, introduces an additional regulating step whereby the sensitivity of the mechanism and its speedof response is improved.

What I claim as new andA desire to secure by Letters Patent of theUnited States is:

l. The combination, in an arc lamp having a pair of electrodes= of means responsive to the arc current for adjusting one of said electrodes relatively to the other during operation, means for establishing a` common electric circuit for supplying operating current to the electrodes and to said adjusting means, and means Within said lamp for supplying current to said adjusting means effective at the instant the operating current in said common circuit isinterrupted during normal, operation, thereby to effect a continuation of the operation of saidadjusting means after the interruption of the normal supply current.

2. The combination, in an arc lamp having a pair. of electrodes, of means for adjusting one of said electrodes relatively to the other during operation of the lamp, a common electric supply circuit for supplying operating currentto the electrodes and to said adjusting means, a motor, reversing mechanism through which the motor operates said adjusting means to move one electrode toward the other, and means effective at the instant at which the current in said common electric supply circuit is interrupted during normal operation of the lamp to provide the electric current necessary to effect an actuation of said reversing mechanism.

3. In an arc lamp for a searchlight including a negative and a positive electrode, the combination of an electrode feed mechanism operable alternatively to advance and to retract one of saidelelctrodes, a1A motor,"means,y for connecting electrodes, magnet coils arranged to be connectedl across a part of said potentiometer resistor and to operate said means for connecting saidmotor to drive said electrode mechanism respectivelyv to advance and to retract said electrode, and means responsive to variations in a4 characteristic of the arc arranged to close a circuit between said potentiometer resistor and said magnets respectively to effect an energization of` said coils respectively.

4. In an arc lamp for a searchlight the,V combination of a negativeand a positive electrode, a negative electrode feed mechanism operable alternatively to advance and to retract said negative electrode, a motor, means for connecting said motor todrive said negative electrode feed mechanism, a potentiometer resistor connectedl across the said electrodes, magnet coils arranged tobe connected across a part of said potentiometer resistor and when energized to operate said means for connecting said motor to drive said negative electrode mechanism respectively to advance and to retract said electrode, and means responsive to variations in a characteristic of the arc arranged to close a circuit between said` potentiometer resistor and said magnets respectively to effect an energization of said coils respectively.

5. In an arc lamp for. a searchlight including a negative and a positive electrode, the combination of an electrode feed mechanism operableto advance one of saidelectrodes, a motor, a clutch device for connecting said motor to drive said electrode mechanism, a potentiometer resistor connected across the said electrodes, magnet coils arranged to be connected across a part of said potentiometer resistor and to operate. saidclutch device to effect an operation of said electrode mechanism to advance said electrode, meansA responsive to variations in a characteristic of'the arc arranged to eiect a periodicy closure of a circuit between said potentiometer resistor and said magnet thereby effecting an intermittent energization of said coil, said means being operable upon a predetermined greater variation in the are characteristic to effect a continuousfclcsure of said circuit.

6. In an arc lamp for a searchlight, the combination of a negative electrode and a positive electrode, a feed mechanism for said negative electrode, a motor electrically connected in multiple with said electrodes, clutch means for con.- necting said motor to drive said negative electrode feed mechanism, a potentiometer resistor connected across said electrodes, avpair of magnet coils arranged to be connected across a part of said potentiometer resistor and when energized to operate said clutch means for connecting said motor to said negative electrode mechanism respectively to advance and to retract said electrode, a group of contacts, means to operate said contacts in response to variations i-n a characteristic of the arc and arranged to close a circuit between said potentiometer resistor and said magnet coils respectively to effect an energiza- -tion of said coils respectively, and a pair of contacts in said group and operated by said means arranged to establish a shunt circuit about a part of said potentiometer resistor under predetermined operating conditions so as to apply substantially the whole available voltage to said magnet coils.

7. In an arc lamp, the combination of an electrode advance mechanism, a motor provided with a predetermined inertia and regenerating characteristic, a clutch mechanism operable to connect said motor to drive said electrode advance mechanism, electroresponsive means for operating said clutch mechanism and means responsive to an interruption of the current in said lamp for connecting said electroresponsive means in circuit with said motor, whereby upon a sudden interruption of supply current to said motor during operation the motor is both mechanically and electrically connected to apply its kinetic energy to advance the electrode to substantially its starting position.

8. In an arc lamp, the combination of an electrode advance mechanism, a motor provided with a predetermined inertia and regenerating characteristic and electrically connected to the circuit of the arc lamp, a clutch mechanism operable to connect said motor to drive said electrode advance mechanism, electroresponsive means for operating said clutch mechanism, means responsive to an interruption of the arc for connecting said electroresponsive means in circuit with said motor, whereby upon the interruption of the current to the arc lamp during operation the said motor and said electroresponsive means being connected in circuit with each other the regenerated current from said motor fiows through and energizes said electroresponsive means to effect a closure of said clutch and the electrode advance mechanism is operated until the kinetic energy of the motor is spent.

9. In an electrode regulating mechanism, the combination of a positive and a negative electrode, feed rolls for axially moving one of said electrodes, a motor electrically connected in circuit With said electrode, a clutch device operable to connect said motor to operate said feed rolls, a magnet arranged to operate said clutch device to eiect an advance of said electrode, means responsive to a cessation of the arc current for establishing an electric circuit between said motor and said magnet, said motor being provided with armature inertia and regenerating characteristic of such magnitude as to energize said magnet and to eiect an operation of said electrode moving mechanism in a direction to advance said electrode toward its starting position subsequent to a cessation of current through the electrodes during operation, whereby the subsequent starting period between resumption of current flow and the arc ignition is correspondingly reduced.

10. In an arc lamp, the combination of an electrode, feed rolls operable to advance said electrode, a motor, a clutch device operable to connect said motor to operate said feed rolls to advance said electrode to starting position, a magnet coil arranged to operate said clutch device to eect an advance of said electrode, means responsive to a cessation of the current flowing through said lamp for closing the circuit to said magnet, a fan motor normally connected in circuit with said iirst mentioned motor and connected in circuit with said magnet upon an interruption of current in said lamp, said fan motor being provided with armature inertia and regenerating characteristic of such magnitude as to energize said magnet and thereby effect an operation of said clutch, whereby upon a simultaneous interruption of current to both said motors the electrode moving mechanism is operated by the kinetic energy of said first-mentioned motor in a direction to advance said electrode toward its starting position subsequent to an interruption of current to said lamp, the subsequent starting period between resumption of current flow and the arc ignition being correspond` ingly reduced.

11.111 an arc lamp, the combination of an electrode circuit, an electrode advance mechanism, a motor having a predetermined inertia and regenerating characteristic, a circuit therefor, a clutch device operable to connect said motor to drive said electrode advance mechanism, electroresponsive means for operating said clutch device, means responsive to an interruption of the arc for connecting said electroresponsive means in circuit with said motor to energize said electroresponsive means and effect an operation of said clutch, and a common switch for said electrode and motor circuits, whereby upon the opening of said common switch during operation of said lamp the said motor and said electroresponsive means being connected in circuit with each other the regenerated current from said motor flows through and energizes said electroresponsive means to eiect a closure of said clutch whereby the electrode advance mechanism is operated until the kinetic energy in the motor is spent.

12. In an arc lamp, the combination of a negative electrode, feed rolls operable to advance said negative electrode, a driving motor, a clutch device operable to connect said driving motor to operate said feed rolls to advance said negative electrode to starting position, a magnet coil arranged to operate said clutch device to effect an advance of said electrode, means responsive to a cessation of the current flowing through said electrode for closing the circuit to said magnet coil, an auxiliary motor normally connected in circuit with said electrode and connected in circuit with said magnet coil upon an interruption oi current in said lamp, said auxiliary motor being provided with armature inertia and regenerating characteristic of such magnitude as to energize said magnet coil and thereby effect an operation of said clutch upon an interruption of supply current during normal operation, whereby the electrode moving mechanism is operated by the kinetic energy of said driving motor in a direction to advance said electrode toward its starting position subsequent to an interruption of current to said lamp.

LYLE A. SHELDON. 

